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mercurial: implement import hook for handling C/Python modules...
mercurial: implement import hook for handling C/Python modules There are a handful of modules that have both pure Python and C extension implementations. Currently, setup.py copies files from mercurial/pure/*.py to mercurial/ during the install process if C extensions are not available. This way, "import mercurial.X" will work whether C extensions are available or not. This approach has a few drawbacks. First, there aren't run-time checks verifying the C extensions are loaded when they should be. This could lead to accidental use of the slower pure Python modules. Second, the C extensions aren't compatible with PyPy and running Mercurial with PyPy requires installing Mercurial - you can't run ./hg from a source checkout. This makes developing while running PyPy somewhat difficult. This patch implements a PEP-302 import hook for finding and loading the modules with both C and Python implementations. When a module with dual implementations is requested for import, its import is handled by our import hook. The importer has a mechanism that controls what types of modules we allow to load. We call this loading behavior the "module load policy." There are 3 settings: * Only load C extensions * Only load pure Python * Try to load C and fall back to Python An environment variable allows overriding this policy at run time. This is mainly useful for developers and for performing actions against the source checkout (such as installing), which require overriding the default (strict) policy about requiring C extensions. The default mode for now is to allow both. This isn't proper and is technically backwards incompatible. However, it is necessary to implement a sane patch series that doesn't break the world during future bisections. The behavior will be corrected in future patch. We choose the main mercurial/__init__.py module for this code out of necessity: in a future world, if the custom module importer isn't registered, we'll fail to find/import certain modules when running from a pure installation. Without the magical import-time side-effects, *any* importer of mercurial.* modules would be required to call a function to register our importer. I'm not a fan of import time side effects and I initially attempted to do this. However, I was foiled by our own test harness, which has numerous `python` invoked scripts that "import mercurial" and fail because the importer isn't registered. Realizing this problem is probably present in random Python scripts that have been written over the years, I decided that sacrificing purity for backwards compatibility is necessary. Plus, if you are programming Python, "import" should probably "just work." It's worth noting that now that we have a custom module loader, it would be possible to hook up demand module proxies at this level instead of replacing __import__. We leave this work for another time, if it's even desired. This patch breaks importing in environments where Mercurial modules are loaded from a zip file (such as py2exe distributions). This will be addressed in a subsequent patch.

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hgweb.txt
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Mercurial's internal web server, hgweb, can serve either a single
repository, or a tree of repositories. In the second case, repository
paths and global options can be defined using a dedicated
configuration file common to :hg:`serve`, ``hgweb.wsgi``,
``hgweb.cgi`` and ``hgweb.fcgi``.
This file uses the same syntax as other Mercurial configuration files
but recognizes only the following sections:
- web
- paths
- collections
The ``web`` options are thoroughly described in :hg:`help config`.
The ``paths`` section maps URL paths to paths of repositories in the
filesystem. hgweb will not expose the filesystem directly - only
Mercurial repositories can be published and only according to the
configuration.
The left hand side is the path in the URL. Note that hgweb reserves
subpaths like ``rev`` or ``file``, try using different names for
nested repositories to avoid confusing effects.
The right hand side is the path in the filesystem. If the specified
path ends with ``*`` or ``**`` the filesystem will be searched
recursively for repositories below that point.
With ``*`` it will not recurse into the repositories it finds (except for
``.hg/patches``).
With ``**`` it will also search inside repository working directories
and possibly find subrepositories.
In this example::
[paths]
/projects/a = /srv/tmprepos/a
/projects/b = c:/repos/b
/ = /srv/repos/*
/user/bob = /home/bob/repos/**
- The first two entries make two repositories in different directories
appear under the same directory in the web interface
- The third entry will publish every Mercurial repository found in
``/srv/repos/``, for instance the repository ``/srv/repos/quux/``
will appear as ``http://server/quux/``
- The fourth entry will publish both ``http://server/user/bob/quux/``
and ``http://server/user/bob/quux/testsubrepo/``
The ``collections`` section is deprecated and has been superseded by
``paths``.
URLs and Common Arguments
=========================
URLs under each repository have the form ``/{command}[/{arguments}]``
where ``{command}`` represents the name of a command or handler and
``{arguments}`` represents any number of additional URL parameters
to that command.
The web server has a default style associated with it. Styles map to
a collection of named templates. Each template is used to render a
specific piece of data, such as a changeset or diff.
The style for the current request can be overwritten two ways. First,
if ``{command}`` contains a hyphen (``-``), the text before the hyphen
defines the style. For example, ``/atom-log`` will render the ``log``
command handler with the ``atom`` style. The second way to set the
style is with the ``style`` query string argument. For example,
``/log?style=atom``. The hyphenated URL parameter is preferred.
Not all templates are available for all styles. Attempting to use
a style that doesn't have all templates defined may result in an error
rendering the page.
Many commands take a ``{revision}`` URL parameter. This defines the
changeset to operate on. This is commonly specified as the short,
12 digit hexadecimal abbreviation for the full 40 character unique
revision identifier. However, any value described by
:hg:`help revisions` typically works.
Commands and URLs
=================
The following web commands and their URLs are available:
.. webcommandsmarker